Rotary drill cutter



Nov. 2, 1943. I BEHNKE 2,333,407

ROTARY DRILL CUTTERS Filed July 11, 1940 g 2 7 uy EiBelm/re INVENTOR Patented Nov. 2, 1943 UNITED STATES PATENT cri ic- E ROTARY DRILL CUTTER:

Guy -E. Hehnke, Oklahoma City, Okla... assignorlto. Chicago Pneumatic ToolC'ompany, New York, 'N. Yr, a'corporati'on'. of New Jersey ApplicationiJiily ll, 1940,1Scria1;No...344,855o

2JCl'aims.. (Cl. 255- 7'1) This invention-relates generally to roller cutterszfor use-in earth .b'oring bit assemblies,;iand more particularly to the toothformationof such cuttersr Oneobje'ct of the-invention is to enable-abit assembly 1 to function effectively under relatively light drilling pressure.

Another object of the invention is to obtain coarse cuttings -of thematerial being cut in order thatthevariousformations encountered in drilling a well may be *easilyiden-tified' and correctly I logged.

According to the present invention these objects are attained through adistribution of-the cutting .teethamongthe several'cutters of a'bit assemblywhich effects areduction in cutting area andiso spaces certain rows of teeth that these teeth act to chipor loosen some material from the formation instead of disintegrating it.

Another objectof the invention is to obtain a distribution of cutting teeth that will ofier the least resistance to penetration and still provide for uniform Wear.

A feature of this aspect of the invention lies in an arrangement of teeth at the apex portion of the cutter which permits these teeth also to penetrate deeply into the earth formation.

Other objects and structural details of the invention will be more apparent from the following description when read in conjunction with the accompanying drawing, wherein:

Fig. 1 is a view partly in elevation and partly in longitudinal section of a bit assembly embodying the cutter construction of this invention; and

Fig. 2 is a View of the assembly shown in Fig. 1, looking upward from below the assembly.

The invention is disclosed as embodied in a bit assembly of the type having three cooperating roller cutters of generally conical shape. It should be understood, however, that this disclosure is merely illustrative since the invention may be embodied in bit assemblies having a greater or lesser number of cutters than three.

Referring to Fig. 1 of the drawing the assembly comprises a split type bit head I having an upwardly extending shank II adapted for threaded engagement with a rotary drill stem. The lower end of the bit head is formed with three separate depending portions I2 each of which carries a bearing (not shown) supporting a roller cutter I3. The cutters I3 are generally conical in shape, extend inwardly towards the longitudinal axis of the bit head If) and are arranged with their longitudinal axes perpendicuof relativelywide I teeth It 1 which maintainthagauge of thedrill' hole and cut clearance for? the. bit head. lTl'ie teeth M are fo-rmed ona peripli eral zone G5 which tapers inward-towar'd- 'animaginary apex which=is in line-with the axisof rotation of the-cuttter-and iar beyond theaxis of revolution of the bit. The zone I5 merges with another zone I6 tapering at a less acute angle toward an apex substantially at the intersection of the cutter and bit axes. Zone I6 comprises an apex portion H3 at its tip, and an intermediate portion extending between said apex portion and the zone l5. Each cutter has one or more circumferential rows of pyramidal or pick-point teeth I! arranged on the intermediate portion of the cutter. Preferably, one of the rows on one cutter is positioned at the intersection of the zone I6 with the base zone I5. Formed on the apex portion I3 of each cutter is a pair of blade-like teeth I9 and two sets of pyramidal shaped teeth 2|. The teeth I9 are oppositely disposed 0n the apex portion I8 and have respective longitudinal cutting edges which taper inward to a point at the very tip of the apex, thereby simulating the shape of a spear point. The sets of teeth 2| are arranged at the base of the apex portion I8 with the respective sets occupying positions on opposite sides of the apex between the blade-like teeth I9. The apex teeth 2| and intermediate teeth I! are all of approximately the same size and shape and penetrate the formation to substantially the same extent.

The apices of the several cutters lie adjacent one another and substantially adjacent the longitudinal axis of the bit head ID. The apex teeth I9 occupy the same relative positions on all three cutters, and follow the same general path around the center of the drill hole. The pyramidal teeth 2I roll over a part of the area cut by the teeth I9. To prevent the apex portion of one cutter from tracking in the ridges cut by another cutter, it is desirable to provide two cutters with a difierent number of pyramidal teeth 2!. As shown in the drawing, there are four such teeth on one cutter and two on each of the others. Through the cooperation of the several sets of apex teeth the central portion of the hole is cut rapidly and efficiently and the wear incident to the work is distributed evenly among the cutters.

The intermediate rows of teeth I! are so distributed among the cutters as to cut away by their combined action the earth formation between the base teeth l4 and the apex teeth l92 I. The row or rows of teeth on each cutter are offset with respect to corresponding rows on the companion cutters and follow a separate path along the bottom of the drill hole. Unlike-the conventional cutters of this type, however, the

rows of teeth I1 do not combine to cut adjacent paths but are so spaced as to cut paths separated from each other by uncut ridges of formation. In brittle formations these uncut ridges chip and ar readily broken up into coarse relatively large cuttings. The non-true rolling motion of the cutter results in a slight twisting movement by the teeth as they penetrate, thereby facilitating the chipping action. In shales and hard packed clays the side wallsof the teeth I! press against the uncut ridges and so loosen the formation as to permit it to be carried away by the usual hydraulic flushing means. This spacing of the rows of teeth I! results in a reduction in cutting area and a corresponding increase in cutting speed. The increased cutting speed is obtained because the weight of the drill is concentrated upon a smaller supporting area, thus causing a deeper penetration of the teeth. Since some earth formations are more readily chipped than others the spacing of the rows of teeth I! is determined by .the kind of formation being out. To obtain the ferently constructed cutter assemblies may be provided for selective use.

It will be further noted that the reduction in cutting area permits eflective use of the bit assembly under less weight than is necessary for operation of the conventional assembly. It is a well known fact that excessive weights tend to cause the cutters to follow inclined formation strata and depart from the desired course through the earth.

What is claimed is:

1. A bit assembly comprising a bit head, a plurality of generally cone shaped roller cutters supported on said bit head, each of said cutters having an apex portion lying adjacent the longitudinal axis of said bit head, a plurality of bladelike teeth formed on said apex portion, said teeth tapering from rearmost points of maximum height at the base of said apex portion inward toward the axis of the cutter and terminating adjacent the tip of said apex portion, a plurality of pyramidal teeth formed on the base of said apex portion defining in cooperation with the rearmost points of said b1ade-like teeth an inner circumferential row of pointed teeth, and an outer circumferential row of teeth on each or said cutters, the teeth of which conform in size and shape to the teeth of said inner row.

2. A bit assembly according to claim 1, charac-. terized in that each of said inner circumferential rows of teeth is spaced a distance from the longitudinal axis of said bit head causing-it to move in the same path followed by corresponding rows of teeth on the companion cutters, while each of the outer circumferential rows of teeth is spaced a distance from the longitudinal axis of said bit head causing it to move in a path spaced from the paths followed by corresponding rows of teeth on the companion cutters.

GUY E. BEHNKE. 

